Non-staining metal working lubricant



NON-STAINING METAL WORKING LUBRICANT Ernst Lang, Union City, N. 3., assignor to Socony Mobil Oil Company, Incorporated, a corporation of New York No Drawing. Application August 18, 1954, Serial No. 450,815

9 Claims. (Cl. 25234.7)

This invention relates to an improved lubricating com: position and more particularly to a composition especially adapted for lubricating metals during processing operations such as cutting, drilling, tapping, mil-ling, rolling, drawing, and the like. By way of conventional designation in the art, the lubricating compositions with which the present invention is concerned fall within the class commonly referred to as soluble oils. These, as is well known, comprise a lubricating oil having dissolved or dispersed therein an emulsifying material imparting 'to the oil a capacity for substantial aqueous dilution to form a stable emulsionof oil and water.

The emulsion so formed is utilized by pouring over the tool and-the work in a steady stream and functions to dissipate the heat from both the tool and the Work;

improve the quality of the work produced; lubricate the.

surfaces in contact between the tool and the work; wash away the chips; and to provide lubrication between the chip and the tool, thus reducing the pressure of the chip on the tool.

It has been a prevalent problem in the machining of non-ferrous metals utilizing a soluble oil emulsion to attain a resulting machined product free of stain. Thus, it has heretofore been observed in the working of copper and aluminum that the machined product often has a stain or discoloration ttributable to the soluble oil emulsion employed. Such discoloration of the metals has been objectionable particularly when the same are used for display, artistic, or decorative purposes. The problem of making a stain-free aluminum sheet has been a difiicult one for a number of years. Some suggestions have been made of incorporating in the soluble oils, sulfonates and amine soaps to counteract the tendency of the metals to become discolored during contact with the soluble oil emulsions. Such suggestions, however, have not proved to be acceptable commercially and the problem of staining of non-ferrous metals has remained and, in fact, has become increasingly important with greater widespread industrial use of these metals.

It is accordingly an object of the present invention to provide an improved compositions adapted for lubrication, during metal processing operations, free of the aforesaid disadvantages. A further object is to provide an improved metal processing lubricant which is non-staining towards non-ferrous metals. A still further object is the provision of a commercially attractive emulsifiable oil composition.

The above and other objects which will be apparent to those skilled in the art are attained in accordance with the present invention which comprises a soluble oil containing a small amount of oxalic acid. It has been found that the resulting compositions are effective 'lu bricants for metal processing operations and afford nonstaining lubricants useful in various machining operations of non-ferrous metals including cutting, rolling, tapping, milling, and the like.

It has been discovered, in accordance with the instant invention that soluble cutting oils can be rendered nonstaining towards non-ferrous metals by the presence therein ofa small amount. of oxalicacid. The characterizing ingredients of the present composition accordingly include a basic lubricating oil, an emulsifyingagent present in a proportion capable of promoting the formation of an oil-in-water emulsion and a small amount of a nonstaining agent of oxalic acid.

As an example of. the emulsifiable soluble oil compositions of this invention, the following is representative:

The procedure for the preparation of the above emulsifiable lubricant is, as follows: the oxalic acid, water, and diethylene glycol are mixed to form a homogeneous solution. Thereafter, the remaining components are com.- bined in any sequence desired at ambient temperatures. In those compositions wherein water is absent, the oxalic acid may be dissolved directly in diethylene glycol. It

is also feasible in accordance with this invention to add the oxalic acid directly to the aqueous emulsion resulting from dilution of the soluble oil instead of incorporating the oxalic acid into the, parent soluble oil. In

proceeding in accordance with the latter alternative, a1"- ready prepared soluble oils maybe rendered non staining towards non-ferrous metals. 7 K n V The emulsifier employed in the composition may com prise any of the conventional alkali metal or aminesoaps or mixtures theerof customarily employed in solubleoils'j and capable of promoting the formation of {an oil-inwater emulsion, such as natural or synthetic carboxyl'ates g sulfonates, resinates, and naphthenates, In addition, the; various synthetic or: non-soap emulsifiers which are well known in the detergent field, including-the hexahydric alcohol partial esters of high molecular weight fatty acids and the anhydride's thereof, such as sorbitan mono-oleate,

can also be employed for this purpose either alone on in combination with a soap emulsifier. A very typical and usual material of this type is a soap ofa long chain fatty acid. Thus, in the above illustrated composition, the oleic acid and glyoxalidine reactant'in combination formed a soap which served as an emulsifier. In place of oleic acid, a long chain fatty acid of l2or more carbon atoms may be employed. In place ,of l-hydroxyethyl', 2-heptadecenyl glyoxalidine, various other glyoxalidines.

such as l-amino ethyl, Z-heptadecenyl' glyoxalidine may be employed conforming to the (type formula:

wherein R1 is selected from the groups consisting of alkyl and alkenyl radicals containing from 10 to 18 carbon atoms; R2 is an alkyl group containing le'ssthan' 5 carbon atoms substituted with a radical X selected from; thegroup consisting of hydroxyl and aminoiradicalsg Likewise, sodium or'p ot assium soaps of animal andvegea table fats may similarly be employed. Numerous other-- common emulsifying'agents, such as'the alkali soaps of resin, oleic acid, naphthenic. acids, etc.,;ma;y also housed.

' These emulsifying agents may either be prepared in situ as theamine soap above or employed in already prepared form. It is generally desirable, but not essential, to have emulsifiers of the cationic and non-ionic type present in the soluble oil composition. Thus, in

the foregoing example, the-soap of the glyoxalidihe ,re--

ajctant functioned as a cationic emulsifier while the polyoxyethylene octylphenol reactant functionedas a nonionic type emulsifier. It will be realized that, in place of polyoxyethylene octylphenol, other. non-ionic type emulsifiers may be used. Representative of this class of emulsifiers are alkylated aryl poly-ether alcohols and particularly the products of condensation of a phenol or phenol derivative with ethylene oxide. Where the combination of cationic and non-ionic type emulsifiers is used, the former is usually present in the approximate range of-4 to-30 percent by weightof'the soluble oil and the latter type emulsifier present in the approximate range of 1 to 10 percent by weight-of thesoluble oil. The proportion of the emulsifying agent may be varied widely and will be largely dependent upon the effectiveness thereof as an emulsifying agent. For practical purposes, it will be understood that the emulsifying agent is present in a minor proportion sufiicient to provide a substantially stable emulsion, generally between about and about 40 percent by weight of soluble oil.

The base oil of the soluble emulsifiable oil composition may comprise a mineral, animal, and/or vegetable oil. Preferably a hydrocarbon oil and particularly one having a Saybolt Universal viscosity at 100 F. in the range of about 40 to about 200 seconds and an- A. P. I. gravity of 19 to 36 is employed.

4 As is well known, soluble oils are usually prepared in the form of a colloidal solution containing a minimum quantity of water to enable the oil, at the time of use, to rapidly take up additional quantities of water to form the dilute emulsions customarily employed for the cooling and lubrication of the metal working operations. In order to form a concentrated soluble oil of this character which is stable in storage against separation of ingredients, a small proportion of the order 0.5 to 5 percent by weight of a coupling agent is added to the soluble oil. Examples of very satisfactory coupling agents are monohydric alcohols, polyhydn'c alcohols, and alcohol ethers such as ethanol, propanol, isopropanol, butanol, amyl alcohol, diethylene glycol, diethylene glycol monobutyl ether, etc. It is usually advantageous to employ a coupling agent, but it is not always necessary.

The concentration of oxalic acid in the soluble oil com positions is such as to render the same non-staining and may be varied widely in accordance with the use to which it is to be put. Where the emulsion is to be employed as a coolant, as well as a lubricant, and applied by a circulating pump or the like, the oxalic acid should ordinarily be present in a concentration of .001 to .8 percent by weight. Generally, the emulsion will be marketed as a concentrate to be further diluted for use as required. In such concentrate the oxalic acid will usually be present in a concentration of 0.1 -to 4 percent by weight of the soluble oil. Thus, the composition of the present invention contemplates the presence of oxalic acid in soluble oils and resulting emulsions in amounts etfective to render the composition non-staining toward non-ferrous metals and in particular aluminum and copper.

The emulsifiable oil compositions of this invention ac cordingly comprise the combination of recited components in the following proportions:

I In some instances, it may be desirable to include antiparts by volume of Water.

septic, bactericidal, or other inhibitive agents in the soluble oil compositions.

The above emulsifiable oil compositions are generally diluted with water to obtain the soluble oil emulsions. Thus, the working emulsion may be obtained from the above soluble oil composition by diluting 1 part by volume of soluble oil with from approximately 5 to 100 The extent of dilution will generally depend on the operation wherein the resulting emulsion is to be used. Thus, for rolling operations, 1 part of soluble oil is conveniently diluted with about 32 parts of water, while for cutting operations, it is preferred to dilute 1 part of soluble oil with approximately 14 parts of water.

An evaluation of the staining qualities of a typical soluble oil emulsion with and without oxalic acid was obtained by subjecting samples of the oils to the following test: -A 2% x 18" x .009" piece of aluminum sheet is rolled into a coil and placed upright in a 150 cc. glass beaker. The coil is then wetted with 5 drops of an emulsion resulting from dilution of 1 part by volume of soluble oil with 32 parts by volume of water placed in 5 different spots on the upper edge of the coil. The whole assembly is then placed in an electric oven and held at 220 F. for 6 hours. After this exposure, the beaker with the coil is removed from the oven and cooled to room temperature. The coil is then unwound and inspected for stains. The soluble oil composition set forth above as exemplary of the compositions of this invention was tested for staining characteristics and gave excellent results. The sheet in such test had no stains. The test experiment repeated with the identical soluble oil composition but without oxalic acid showed excessive staining.

From the foregoing, it will be seen that the presence of a small amount of oxalic acid in the soluble oil composition had the effect of eliminating metal staining.

It is to be understood that the above description is merely illustrative of preferred embodiments of the invention, of which many variations may be made by those skillecll in the art without departing from the spirit thereof.

I c aim:

1. An emulsifiable oil composition consisting essentially of a major proportion of a lubricating oil selected from the group consisting of mineral, animal, and vegetable oil, a minor proportion of an emulsifying agent capable of promoting the formation of an oil-in-water emulsion and a small amount of oxalic acid sufiicient to impart nonstaining qualities toward non-ferrous metals.

'2. Anemulsifiable oil composition consisting essentially of about 45 to about percent by weight of a lubricating oil selected from the group consisting of mineral, animal, and vegetable oil, about 5 to about 40 percent by weight of an emulsifying agent capable of promoting the formation of an oil-in-water emulsion and about 0.1 to about 4 percent by weight of oxalic acid.

3. An emulsifiable oil composition consisting essentially of about 45 to about 95 percent by weight of a lubricating oil selected from the group consisting of mineral, animal, and vegetable oil, about 5 to about 40 percent by weight of an emulsifying agent capable of promoting the formation of an oil-in-Water emulsion, about 0.5 to about 5 percent by weight of a coupling agent selected from the group consisting of monohydric alcohols, polyhydric alcohols, and alcohol ethers, and about 0.1 to about 4 percent by weight of oxalic acid.

4. An emulsifiable oil composition consisting essentially of about 45 to about 95 percent by weight of a lubricating oil selected from the group consisting of mineral, animal, and vegetable oil about 4 to about 30 percent by weight of a cationic emulsifier, about 1 to about 10 percent by weight of a non-ionic emulsifier, said emulsifiers being characterized by the ability to promote the formation of an oil-in-water emulsion, and about 0.1 to about 4 percent by weight of oxalic acid.

5. An oil-in-water emulsion consisting essentially of one part by volume of the composition defined in claim 2 diluted with 5 to 100 parts by volume of water.

6. An oil-in-water emulsion consisting essentially of one part by volume of the composition defined in claim 3 diluted with 5 to 100 parts by volume of water.

7. An aqueous soluble cutting oil emulsion consisting essentially of mineral lubricating oil dispersed in water, an emulsifying agent present in minor proportion sulficient to form a stable oil-in-water emulsion and between about .001 and about 0.8 percent by weight of oxalic acid.

8, An aqueous soluble cutting oil emulsion consisting essentially of a lubricating oil selected from the group consisting of mineral, animal, and vegetable oil dispersed in water, an emulsifying agent present in minor proporion sufiicient to form a stable oil-in-water emulsion and a small amount of oxalic acid sufficient to impart nonstaining qualities toward non-ferrous metals.

9. A composition capable of forming a stable aqueous emulsion upon dilution with water consisting essentially of the following components:

References Cited in the file of this patent UNITED STATES PATENTS 1,954,745 Peterson Apr. 10, 1934 2,470,913 Bjorksten et al May 24, 1949 FOREIGN PATENTS 495,922 Canada Sept. 8, 1953 OTHER REFERENCES Synthetic Organic Chemicals, publication of Carbide and Carbon Chemicals Corp., New York, N, Y., 12th 20 edition, July 1, 1945, page 81. 

1. AN EMULSIFIABLE OIL COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF A LUBRICATING OIL SELECTED FROM THE GROUP CONSISTING OF MINERAL, ANIMAL, AND VEGETABLE OIL, A MINOR PROPORTION OF AN EMULSIFYING AGENT CAPABLE OF PROMOTING THE FORMATION OF AN OIL-IN-WATER EMULSION AND A SMALL AMOUNT OF OXALIC ACID SUFFICIENT TO IMPART NONSTAINING QUANLITIES TOWARD NON-FERROUS METALS. 